1. Field of Invention
The present invention relates to a method for depositing a film, a device for depositing a film, a device for discharging droplets, a method for manufacturing a color filter, a display device including a color filter, a method for a manufacturing display device, a display device, and an electronic apparatus, and particularly to a technique for depositing a film by discharging droplets.
2. Description of Related Art
Various types of display devices using electro-optic devices, such as liquid crystal display devices and electroluminescent display devices (hereinafter referred to as EL devices), as display means and electronic apparatuses having such a display device, such as cellular phones and personal digital assistants, have been generally known. Since it is becoming common that these display devices display color images, the display devices often include a color filter in which R (red), G (green), and B (blue) dots serving as filter elements are arrayed on the surface of a substrate formed of glass, resin, or the like in a predetermined arrangement, such as a striped arrangement, a delta arrangement, or a mosaic arrangement.
In an EL device capable of displaying color images, display dots comprising R (red), G (green), and B (blue) dots serving as EL luminescent films disposed in a predetermined arrangement, such as a striped arrangement, a delta arrangement, a mosaic arrangement, or the like between pairs of electrodes are formed on a substrate of glass, resin, or the like. The display dots each emit light having predetermined color and gradation by controlling voltage applied to the electrodes from one display dot to another.
When these display devices are manufactured, the filter elements for colors of the color filter and the luminescent films for colors of the EL device are generally patterned by photolithography. Unfortunately, such a patterning step using photolithography requires complicated, time-consuming treatments, such as material deposition, exposure, and development. Also, the patterning step undesirably consumes a large amount of color materials and resist, consequently increasing costs.
In order to solve this problem, a method has been proposed in which droplets containing a filter element material or an EL luminescent material and a solvent are discharged by an ink jet technique to land on the surface of a substrate, thus forming filter elements or luminescent films arrayed in a dot manner. A process of forming filter elements 303 will now be illustrated in which filter elements 303 are arrayed by a ink jet technique, in a dot manner as shown in FIG. 61(b), in a plurality of unit regions 302 on a so-called mother substrate 301, which is a large-area substrate formed of glass, resin, or the like, as shown in FIG. 61(a).
In this instance, for example, while an ink jet head 306 having a nozzle line 305 comprising a plurality of nozzles 304 as shown in FIG. 61(c) linearly sweeps over each unit region 302 a plurality of times (two times in FIG. 61), as designated by the arrows A1 and A2 in FIG. 61(b), the plurality of nozzles 304 selectively discharge ink, or a filter material, to form filter elements 303 in desired positions.
These filter elements 303 are formed by arraying colors, such as R, G, and B, in a predetermined arrangement pattern, such as a striped arrangement, a delta arrangement, or a mosaic arrangement, as described above. Therefore, it is generally needed to use R, G, and B color ink jet heads 306 one by one in order to form a color filter in a predetermined color arrangement on the mother substrate 301.
In the ink jet head 306, the discharge quantity from the nozzles 304 constituting the nozzle line 305 generally varies. The ink jet head 306 has an ink discharge quality Q in that, for example, nozzles 304 at both ends of the nozzle line 305 offer the largest discharge quantity, nozzles 304 in the center of nozzle line 305 offer the larger discharge quantity, and the other nozzles 304 offer the smallest discharge quantity, as shown in FIG. 62(a).
As a result, when the filter elements 303 are formed with the ink jet head 306, as shown in FIG. 61(b), dense lines, that is, striped color shadings, are formed in either positions P1 at both ends of the ink jet head 306 or positions P2 at the middle of the ink jet head 306, or in both positions P1 and P2. As a result, light-transmission characteristics of the color filter disadvantageously have variation when viewed from above.
Accordingly, a method for reducing the unevenness of film deposition resulting from variation of the discharge quantity of droplets has been known (for example, refer to patent document 1 listed later) in which while sweeping and gradually shifting in the shifting direction (the horizontal direction in FIG. 61(b)), the ink jet head 306 discharges droplets a plurality of times to form each filter element 303 (hereinafter simply referred to as the “error variance” method).
Unfortunately, the error variance method greatly increases the times of sweeping in comparison with the known method even if an identical product is manufactured, thus increasing manufacturing time and reducing production efficiency. Accordingly, in order to solve the problem, a device is proposed (for example, patent document 2 listed below) in which a plurality of heads whose attitudes can be controlled are incorporated into a common carriage so that the heads sweep over a wide range at a time to increase the production efficiency.
[Patent Document 1]
Japanese Unexamined Patent Application Publication No. 2002-221616
[Patent Document 2]
Japanese Unexamined Patent Application Publication No. 2002-273868